1. Field of the Invention
The invention relates to an optical system for a microlithographic projection exposure apparatus and to a microlithographic exposure method.
2. Prior Art
Microlithographic projection exposure apparatuses are used for producing microstructured components, such as, for example, integrated circuits or LCDs. Such a projection exposure apparatus comprises an illumination device and a projection lens. In the microlithography process, the image of a mask (=reticle) illuminated with the aid of the illumination device is projected, via the projection lens, onto a substrate (e.g. a silicon wafer) coated with a light-sensitive layer (photoresist) and arranged in the image plane of the projection lens, in order to transfer the mask structure to the light-sensitive coating of the substrate.
During the operation of a microlithographic projection exposure apparatus, there is a need to set defined illumination settings, i.e. intensity distributions in a pupil plane of the illumination device, in a targeted manner. Alongside the use of diffractive optical elements (so-called DOEs), the use of mirror arrangements is also known for this purpose, e.g. from WO 2005/026843 A2. Such mirror arrangements comprise a multiplicity of micro-mirrors that can be set independently of one another.
Furthermore, various approaches are known to set specific polarization distributions in the pupil plane and/or in the reticle in a targeted manner in the illumination device in order to optimize the imaging contrast.
In respect of the prior art, reference is made in an exemplary fashion to WO 2005/069081 A2, WO 2005/031467 A2, U.S. Pat. No. 6,191,880 B1, US 2007/0146676 A1, WO 2009/034109 A2, WO 2008/019936 A2, WO 2009/100862 A1, DE 10 2008 009 601 A1, DE 10 2004 011 733 A1 and EP 1 306 665 A2.